The rotation sequence is notional, and does occasionally change for various reasons. Often it's for political reasons if some issue is being highlighted in a speech, and for whatever reason, SA X is the right backdrop.

The departure from the normal rotation is because President Trump is scheduled to attend a NATO meeting in Belgium on 25 May and a G7 Summit in Sicily 26-27 May. With USAFA on 24 May, USNA on 26 May, and USMA on 27 May, President Trump was unable to accept offers to speak at any of these ceremonies, understandably so.